The present invention relates to a layer press for sheet-like articles, in particular for folded printed products located essentially horizontally one above the other in a stack.
The general problem with stacking sheet-like articles, in particular folded printed products, is that the stacks are elevated or arched upwards in each case at outer peripheries, in particular along which folds or mutually opposite open edges of the sheet-like articles are arranged, in relation to the height in the center of the stacks. In order to compress the stacks in their layered formation and, if appropriate, to prevent sheet-like articles from flying away as the stack is rotated, it is possible to use so-called layer presses, which act on the uppermost sheet-like article of the stack using a contact pressure element.
A layer press for a printed product is described, for example, in EP-A-0 309 745. The layer press here is part of an apparatus for stacking printed products and is equipped with a pressing apparatus. It is assigned to a stacking shaft and, together with the latter, is mounted in a rotatable manner on a framework. The stacking shaft is bounded in the downward direction by a raisable stacking table on which the printed products end up located. As soon as a predetermined number of printed products ends up located one above the other, piston rods of the pressing apparatus are extended into the stacking shaft, into the region of the corners of the uppermost printed product. The stacking table is then raised and the printed products are pressed against the piston rods. The piston rods are elements of piston/cylinder subassemblies which are arranged on L-profiles which can be pivoted about an axis of rotation counter to the force of a helical spring. As the stacking table is raised and the printed products are pressed, the piston rods with the L-profiles are defected slightly counter to the force of the helical spring, whereupon a position sensor deactivates any further raising action of the stacking table when a certain position is reached. After this, either the entire stacking apparatus is rotated through 180°, in order to deposit further printed products on the rotated stack, or, following lowering of the stacking table, the piston rods with the piston/cylinder subassemblies are moved out of their operating position into a rest position and the stack is transported away.
An object of the present invention is to provide a layer press for pressing and compacting stacks of sheet-like articles which, while being of as straightforward a design as possible, ensures careful handling during pressing of the articles.